6-methylocta-3:5:7-trien-2-one



Patented Aug. 12, 1952 ED" iis rA-rEs PATENT o'FFi-cE i f "1'6IVIETHYIIOC'IA-3:5zl7-Jl ltlEN-2 NE M H ilan' Moi ris fleilbron and Basil Charles- Izeicester :Wee'dongliondon, and Ewart Ray'HcrbertJ ones,

Manchester; England, assignors. to :Gl'axo Lab'- oratoriesLimited,Greenford,rEnglandga'Britisli 7 company a;

No Drawing; Application March .7, 1950,.Serial N0. 148,261. In Great Britain March' 22,1949 7 I V This invention is concerned with improvements in-or relating to thepreparation of a new unsaturated ketone, namely." 6=methylocta-:3: 5 57- .trien-FZ-one, which .may 2 be representedtby :the

According to a further feature of the invention We provide a process for the preparation of a new ketone, namely 6-methylocta-3:5z7-trien-2 We prefer to carry out the process in the pres ence of a suitable diluent which may be an excess of acetone or another organic solvent which is inert to the reactants and the products of the process. The concentration of the carbinol in the reaction mixture is preferably less than 5%. The process is also preferably carried out at temperatures within the range '5080 C. for example at the boiling point of the reaction mixture; for this purpose, where a suitable diluent is used, we prefer to use organic solvents forming with the reactants a mixture having a boiling point within the stated range, thus enabling the temperature of reaction to be readily controlled; examples of organic solvents which may be used as suitable diluents are benzene, petroleum ether, dipropyl ether and dibutyl ether and mixtures of two or more of these solvents.

The process is also preferably carried out in an inert atmosphere, for example in an atmosphere of nitrogen.

B-methylpenta-Z:4-dien-l-ol, which is a new compound may be prepared by any convenient method for example by reacting B-methylpentai-en-l-yn-S-ol (Cyrnerman, Heilbron and Jones, J. C. S., 1945, 90) with hydrogen in the presence 11 Claims. (011260-593) 01": Ia 'ip'alladise'd 1 charcoal .-cata1yst" tfco" wield 3-= "methylpentaT-L1:4edien-3=-ol; athe latter Icarbinol may be isQme'rised -in the "presence of dilute-:acid to yield the desired '3 inethylpenta' -2izf i 'dien-l-ol.

The new compound; I 6 =me'thylocta-3 5 1 7 trien- 2 -one, in the purest form -we h'ave been iable to obtain, shows the following characteristics:

It will readily be understood that the above characteristics were determined on the purest materials We have been able to obtain and that the characteristics quoted may be liable to variation dependant on the purity of the product.

In order that the invention may be well understood the following example is given only as an illustration.

Example (a) 3-methyZpenta-1:4-dien-3-0L-A solution of 3-methylpenta-4-en-1-yn-3-ol (10 g.) (Cymerman, I-Ieilbron and Jones, J. C. S., 1945, in methanol (30 c. c.) was shaken in hydrogen in the presence of a palladium-charcoal catalyst (1 2% Pd) until 2410 c. 0. (20 C. .757 mm.) of gas had been absorbed (equivalent to 1 F.'). After removal of the catalystthe methanol solution was diluted with water and the product isolated with ether in the usual manner. Distillation gave 3-methylpenta-1: l-dien-S-ol (6 B. P. 6872 C./120 mm. n 1.4400. (Found: C, 74.3; H, 10.2. Cal-I requires: C, 73.4; H, 10.25%.)

(b) 3-methyZpenta-2:4-dien-1-oL-A mixture of the above carbinol (5.7 g.) dilute sulphuric acid (360 c. c.; 1% w./w.) and a trace of hydroquinone was shaken in an atmosphere of nitrogen at 20 C. for 4 hours. Isolation of the product with ether and distillation gave 3-methylpenta- 2:4-dien-1-ol (1.5 g.) B. P. 106? C./80 mm. n 14942. (Found: C, 72.95; H, 10.6. Cal-I100 re-' quires: C, 73.4 H, 10.25%.) Light absorption: Maximum 2280 A.; 24500.

(0) 6-methyZocta-c:5:7-trien-2-one.--A solution of 3-methylpenta-2z-dien-l-ol (9.2 g.) and aluminum tert-butoxide (27 g.) in acetone (270 c. c.) and benzene (675 c. c.) was refluxed in nitrogen for 36 hours. Isolation of the product in the usual manner and distillation gave 6- methylocta-3:5:'7-trien-2-one (3.8 g.) B. P. IQ-54 C./l0 mm. n 1.584. (Light ab orption: Maximum A. 5 30,000. Found: C, 79.05; H, 9.15. C9I-I12 requires: C, 79.35;H, 9.15%). The 2:4-

3 dinitrophenylhydrazone crystallised from ethyl acetate in dark red needles, M. P. 204-205 C.

We claim:

1. As a new compound, 6-methylocta-315z7- trien-2-one represented by the following structural formula" I 2. A process for the preparation of G-methylocta-3 :5:'7-trien-2-one, which comprises, reacting 3-methylpenta-2:4-dien-l-ol with acetone in the presence of aluminium tertiary butoxide.

3. A process as claimed in claim 2 in which the reaction is carried out in the presence of an excess of acetone.

4. A process as claimed in' claim 2 in which the reaction is carried out in the presence of an inert organic solvent.

5. A process as claimed in claim 2 in which the -1*ea'ction is carried out in the presence of a solvent selected from the group consisting of, benzene,

petroleum ether, dipropyl ether and dibutyl ether.

6. A process as claimed in claim 2, in which the concentration of the carbinol in the reaction medium is less than 5%.

.7. A process as claimed in claim 2 in which the reaction is carried out at atemperature within the range of from 50-80 C.

8. A process as claimed in claim 4, in which the nature and quantity of said solvent is so selected that the boiling point of the reaction mixture is .acetone and aluminum tertiary butoxide at a I temperature within the range -80 C. in the presence of an inert atmosphere.

11. A process as claimed in claim 10, in which the reaction mixture contains an inert organic solvent.

IAN MORRIS HEILBRON. BASIL CHARLES LEICESTER WEEDON. EWART RAY HERBERT JONES.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,429,411 Jones et al Oct. 21, 1947 OTHER REFERENCES Batty et al.: J. Chem. Soc. (1938 vol). DP. 175-79.

Cyrnerman at 2.1.: J. Chem. Soc. (1945 vol.). pp. -94.

Milas et al.: J. Am. Chem. 800., vol. 70, p. 1292 (1948). 

1. AS A NEW COMPOUND, 6-METHYLOCTA-3:5:7TRIEN-2-ONE REPRESENTED BY THE FOLLOWING STRUCTURAL FORMULA 